A typical thermal printer transfers ink, such as from an ink transfer ribbon, to a substrate to print the substrate. The substrate has first and second opposed major surfaces that are movable through the printer in a downstream direction along a print flow path, it being understood that the print flow path need not be straight. A thermal print head in the print flow path has heater elements operable in response to energy delivered thereto to heat the ink transfer ribbon to transfer ink to the substrate at a print location as the ink transfer ribbon and substrate travel relative to the thermal print head along the print flow path. The printer controller can be coupled to a cutter to control the cutter to sever the substrate following printing of print data onto the substrate.
In one known approach, a thermal printer supplies energy to the print head heater elements of a thermal print head to heat these elements to cause a transfer of ink from an ink transfer ribbon to a substrate to thereby print the substrate. These elements can each be a single pixel positioned in a print array with selected elements being heated to print the desired image on the substrate. The amount of energy required to produce a print of an acceptable quality can depend upon the type of ink transfer ribbon and substrate being used in printing. A common form of printer utilizes one set of print head energy settings for each ribbon/substrate combination that requires a different amount of energy for an acceptable print. Thus, for a specific ribbon/substrate combination a corresponding print head energy setting is used to, in theory, result in the desired amount of energy being applied to the heating elements during printing. However, if a printer is in a battery mode of operation, wherein one or more batteries are being used to supply energy for printing, the printer places a substantial current draw on available battery energy. Discharge of the battery can lead to an insufficient amount of energy being provided to the print head heater elements to produce a print of acceptable quality.
Therefore, a need exists for an improved thermal printer that can be powered by a battery and provide high quality prints, even as the battery voltage drops.